Telephone repeater system



1 Nov, 29, 1927.

. 1,650,723 8. cs. POHLMANN TELEPHONE REPEATER SYSTEM F iled Sept. 11, 1924 Patented Nov, 29, 1927.

STATES PATENT orries.

BRUNO GERHARD POHLMANN, OF SIEMENSSTADT, NEAR BERLIN, GERMANY; ASSIGNOR T0 SIEMENS &, HALSKE, AKTIENGESELLSCHAFT, OF SIEMENSSTADT, NEAR BERLIN,

IGERMANY, A CORPORATION or GERMANY.

rnnnPnoNE REPEATER SYSTEM.

npplicati onefiled September 11, 192 serial "and in Germany September 14, 1523.

My invention relates t6 improvements in damping resistance for this frequency is telephone repeater systems.

Repeater connections are already known in which the selectivity of the transmitters is reduced by the connection of additional damping means for the purpose of obtain- 'ing as uniform a repetition a'spossible of all the frequencies necessary for the con-' versation. V w Such additional damping meansmay cons1st of a shunt impedance comprising in series connection ohmic resistance, inductance and capacity. a

In the drawing aflixed th this specification and forming part thereof shows :I.

Fig. 1, curves explainingthe manner of operation of the improved repeater system.

\ Fig. 2, a diagram of the system. x a

Referring to Fig. 1, A is the amplifica tion curve and B the'damping curve of the line. If, for instance, the amplification should just neutralize the damping of the .line, the amplification-curve is so chosen that it intersects the damping curve in two points which are located outside the frequency range necessary for the clearness of articula improved repeater tion. One of these points is located lower than the lowest frequency the good trans mission, of which is desired and the other higher than the higest frequency to he sat 'isfac torily transmitted.

If the ohmic resistance K according to Fig. 2 alone is connected in parallel with one of the incoming or outgoing transmitter smallest while it increases on the other hand forthe higher and lower frequencies. A curve of about the shape of the curve 3--3, Fig. 1, is then obtained. The ascent of the higher frequencies is, however, not yet sufficient. a

My; invention consists in connecting a condensenC, in parallel with the inductance L as shown in Fig. 2 which condenser is so dimensioned that it is in resonance with the inductance L for frequencies in the neighborhood of the highest frequency in the necessary'speech range, or higher, so that for this frequency the resistance isvery high; that means its damping action isvery small.

An amplification curve corresponding I with the curve l -4, Fig. 1, is then obtained; which within. the desiredj frequency range agrees wellwith the damping CHiVGL':

As appears from the above explanations I given by way of example an essential characteristic is that the shunt resistance. is a resonance structure with a plurality of resonance places. Consequently the same effects may also be attained if another structure consisting of inductivity, capacity and resistance with two or more resonance places 4 is employed. It would, for instance be possible to employ two difierent cross-sections which conslst of a series connection of re-' 7 sistance, inductance and capacity.

coils, for instance parallel with the secondary coil of the incoming transmitter the -amplification curve. is flattened and lowered as a whole so that, for instance, it takes, up the position 2-2 in which it runs along the damping curve over a short range only. If 1 on'the other hand the entire shunt impedance according to Fig. 2 of the drawing,

which consists of the series connection: ohmic resistance K, inductance L and capacity C is connected up and if the inductance and the capacity C are so dimensioned that resonance exists at that frequency for which the greatest reduction of the amplification is desired which generally will be the case with the frequency locate in the middle between the limiting frequencies then the to secure .by Letters Patent is As a matter ofcourse it is possible to produce the effect produced at one place'of the repeater upon the amplification curve by one of the above resonance structures also, by a plurality of structures connected at various places. i

lVhat I claim as myinvention and desire In a transmission system the loss characteristic of which varies non-linearly with frequency in the band of transmitted frequencies, an amplifying repeater and means I associated therewith for compensating for said non'-linear characteristic comprising a circuit connected in shunt relation to' said system and comprising resistance, inductance and capacity elements in series with one another and proportioned to possess series resonance at a point intermediate the extreme frequencies in the transmitted band whereby components of frequencies both 'as the hi hest frequency portion of the lower and higher than the resonance'fretransmitte band whereby the absorption by quency are absorbed from the system to a said shunt circuit as the higher frequencies 10 less extent than components at or near the are approached graduall becomes less.

5 resonance frequency, and means associated Intestimony whereof aflix my signature.

with said shunt circuit tending to make it anti-resonant at a frequency at least as'high BRUNO GERHARD POHLMANN. 

